1. Field of the Invention
The present invention relates to a crawler type traveling apparatus and a pivot shaft used in a bulldozer, a hydraulic shovel and the like.
2. Description of Related Art
Generally crawler type traveling apparatuses are provided in both right and left sides of a work vehicle such as a bulldozer, a hydraulic shovel, and a crawler crane.
In the work vehicle as described above, the crawler type traveling apparatus has the configuration in which a track frame is provided on a main body of the vehicle and a final reduction gear including a sprocket and a hydraulic motor for driving are provided at an end part of this track frame. A hydraulic source and the hydraulic motor provided on the main body of the vehicle are connected to each other through a hydraulic piping arrangement, and when a hydraulic oil is fed from the hydraulic source, the hydraulic motor starts rotation, and in association with rotation of the hydraulic motor, the sprocket rotates to drive a crawler engaged with the sprocket, and thus the work vehicle starts running. With the configuration as described above, a compact crawler type traveling apparatus can be realized.
Further in a vehicle such as a bulldozer in which a traction is made much of, sometimes pivot shafts are provided in both right and left sides of the vehicle for pivotably supporting crawler type traveling apparatuses respectively, and with this configuration, the crawler type traveling apparatuses in the right and left sides can be contacted to the ground surface having three-dimensional undulations and a large traction can be obtained.
In the crawler type traveling apparatus as described above, by providing pivot shafts in both sides of a main body of the vehicle for pivotably supporting the crawler type traveling apparatuses and also providing a final reduction gear and a hydraulic motor at an end part of the track frame, a compact crawler type traveling apparatus capable of generating a large traction can be realized.
With the configuration, however, as a hydraulic motor is provided on a track frame rocking up and down and further a hydraulic source is provided on a main body of the vehicle, the hydraulic motor and the hydraulic source must be coupled to each other with a piping arrangement such as a hydraulic hose and the like having a predetermined length and high flexibility. In this case, the piping arrangement likely contacts sand, rocks, stones and the like during a work and is likely damaged.
For solving the problem as described above, there has been proposed a structure having a hydraulic frame and a final reduction gear each provided on a track frame rocking up and down, in which a hydraulic passage with the piping arrangement connected thereto is formed in a pivot shaft for making configuration of the piping arrangement compact and also for protecting the piping arrangement from earth and sand, rocks and the like (Refer to, for instance, reference 1: LIEBHERR A. G. “Operation and Maintenance Manual PR712 Litronic”, Germany, P.O. Box 54, CH-5415 Nussbaumen, Manual No. IRM-710-06 (pages 2 to 6)).
Further there has been a method of protecting the piping arrangement from earth and sand and rocks by inserting a hydraulic piping connecting a hydraulic motor provided on a track frame rocking up and down to a hydraulic source provided on a main body of the vehicle into a hollow pivot shaft (Refer to, for instance, reference 2: Japanese Utility Model Laid-Open No. HEI 2-113585, pages 3 to 5, FIG. 1)).
The technology disclosed in reference numeral 1 will be described as a related art with reference to the related drawings. It is to be noted that the FIG. 6 is a side view showing a bulldozer having a crawler type traveling apparatus according to the related art, and FIG. 7 is a sectional view showing a principle portion of the crawler type traveling apparatus.
A bulldozer 100 includes a main frame 101 elongated in the longitudinal direction provided at a center thereof, and pivot shafts 102 are provided in the right and left side of this main frame 101 so as to protrude from the main frame 101. Further, a crawler type traveling apparatus 110 is pivotably provided to the pivot shaft 102, in a manner that it can oscillate around the pivot shaft axis P2.
The crawler type traveling apparatus 110 includes a track frame 111, an idler 112, a sprocket 113, a track roller 114, a carrier roller 115, and a crawler 116.
The track frame 111 includes a steel-made frame long in the longitudinal direction like the main frame 101, and is pivotably supported on the pivot shaft 102.
The idler 112 is an idle wheel rotatably provided at a front end part of the track frame 111, and the sprocket 113 is a portion of a final reduction gear (not shown) provided at a rear end part of the track frame 111, and is a driving wheel driven by a hydraulic motor described hereinafter.
The plurality of track rollers 114 are rotatably provided under the track frame 111 respectively, while the carrier roller 115 is rotatably provided above the track frame 111.
The crawler 116 is wound around the idler 112, sprocket 113, track roller 114, and carrier roller 115, and engages the sprocket 113.
When the sprocket 113 is rotated by a hydraulic motor for driving, the crawler 116 moves along an orbit outer from the idler 112, track roller 114, and carrier roller 115 and kicks the ground with a grounding surface to move forward and backward.
A boss portion 121 is provided on the rear side of the track frame 111 as shown in FIG. 7, and the boss portion 121 is rotatably inserted to the pivot shaft 102.
Further a bracket portion 122 extending toward a rear edge side of the track frame 111 is monolithically formed on the boss portion 121, and a final reduction gear 123 including the sprocket 113 is attached to an inner side surface of the bracket portion 122, while a hydraulic motor 124 for driving is attached to an outer side surface of the bracket portion 122.
The pivot shaft 102 is tightened to a side plate 103 of the main frame 101 with a bolt 104 so as to penetrate the main frame 101 from the inside to the outside thereof.
A plurality of hydraulic passages 125, 126, 127, 128 each extending from inside of the vehicle to the outside thereof along the shaft center P2 are formed at a axial center portion of the pivot shaft 102, and a gallery block 129 is attached to an outer end face of the pivot shaft 102.
Connected to this gallery block 129 are a pair of hydraulic hoses 130, 131 extending in parallel to each other. Tips of these hydraulic hoses 130, 131 are connected to a suction port and a discharge port not shown of the hydraulic motor 124, and the base end is connected to the gallery block 129.
The suction port and discharge port of the hydraulic motor 124 are communicated via the hydraulic hoses 130, 131 and gallery block 129 to the hydraulic passages 125, 126 inside the pivot shaft 102, and the hydraulic hoses 105, 106 connected to a suction port and an discharge port of a hydraulic pump disposed inside the main frame 101 and not shown are connected to the hydraulic passages 125, 126.
Further connected to the gallery block 129 are hydraulic hoses 132, 133 with a tip of the hydraulic hose 132 connected to a speed control port (not shown) of the hydraulic motor 124 and the hydraulic hose 133 connected to a brake release port (not shown) of a parking brake 123A of the final reduction gear 123. These hydraulic houses 132, 133 are communicated via the gallery block 129 to the hydraulic passages 127, 128 in the pivot shaft 102, and further the hydraulic hoses 107, 108 connected to an operation valve (not shown) provided inside the main frame 101 are connected to the hydraulic passages 127, 128.
An outer side of the bracket portion 122 is covered with a cover 134, and the hydraulic hoses 130 to 133 and the gallery block 129 are protected by this cover 134.
In the configuration of the crawler type traveling apparatus 110 as described above, the hydraulic motor 124 is first provided outside the vehicle in the bracket portion 122 at a rear edge of the track frame 111. On the other hand, required ports of hydraulic appliances such as a hydraulic pump inside the main frame 101 are communicated via the hydraulic passages 125 to 128 in the pivot shaft 102 to the gallery block 129 attached to an outer end face of the pivot shaft 102, and further the gallery block 129 and the hydraulic motor 124 are connected to each other with short hydraulic hoses 130 to 133, so that configuration of the crawler type traveling apparatus is compact.
The crawler type traveling apparatus 110 described in reference document 1 has, however, the problems as described below because the hydraulic motor 124 is on the more outer side of the vehicle body as compared to the final reduction gear 123 including the sprocket 113.    (1) An outer side surface of the crawler type traveling apparatus 110 often contacts obstacles such as surrounding ground or pavement when moving forward and backward or turning, and further often impinges against rolling rocks from a mucking mound and/or rolling rocks from a wall surface of a bench-cut. For this reason, the hydraulic motor 124, hydraulic hoses 130 to 133 provided on an outer side surface of the crawler type traveling apparatus 110 are often damaged even when the components are covered with the cover 134.    (2) The depth of each of the hydraulic passages 125 to 128 formed in the pivot shaft 102 must be great so as to reach the inside of a side plate 103 from the outer end face of the pivot shaft 102 to. Therefore, specific machines such as, a gun drill and extended machining time are necessary for forming the hydraulic passages 125 to 128.